Many patents have been issued pertaining to the manufacture of magnetic Winchester hard discs for computers and the like. Such giants of the industry as Memorex, Dysan, Charlton Associates and Nashua in the U.S.A., and other companies in Japan are producing such products.
In general the standard practice in the industry is to deposit a slurry of magnetic oxides (or magnetic metal particles) in an organic solvent system containing dissolved reactive epoxy resin and a phenolic curing agent. The organic solvent is evaporated and then the metal plate is heated to an elevated temperature to effect the cure of the epoxy resin binder system.
In such a process the disadvantages are obvious. The evaporation of organic solvents into the atmosphere creates significant air pollution. It is expensive in terms of loss of costly solvent, not to mention the possibility of fire and explosion hazard and the concomitant higher insurance costs. In instances where solvent recovery systems are employed there is the additional expense of the capital investment as well as the continuing operating costs.
If there is no recovery system, the loss of solvent due to volatilization, is not only a health hazard to workers, but is of great expense to the manufacturer. Also the fire and explosion hazard effects insurance costs. Air pollution prevention means, such as scrubbers for removal of organic vapors are high in cost.
There is a need, therefore, for a mechanism to reduce such added manufacturing costs. Such a procedure is found in the instant invention which eliminates the use of organic solvents.
It is an object of this invention to provide a binder system for use in the manufacture of and disks which system is free from organic solvent.
It is another object to provide a binder system for magnetic particles for hard disks comprising a aqueous dispersion.
Yet another object is to provide a water based binder for pigment particles that gives rise to excellent adhesion between said particles and the coating substrate (base), i.e. the metal plate.
It is a yet further object to prepare a water based dispersion magnetic media that is suitable for disks used on Winchester drives of all sizes, 14, 8, 51/4 and 31/2 inch.
A still further object is to provide lower cost, high quality rigid metallic discs.
Other objects of the invention will in part be obvious and will in part appear hereinafter.
The invention accordingly comprises the several steps and the relation and order of one or more of such steps with respect to each of the others and the product possessing the features, properties and relation of elements which are exemplified in the following detailed description and the scope of the application of which will be indicated in the appended claims.
For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description.